Thermostat and testing machine provided with the same

ABSTRACT

A thermostat includes a plate body, a heat insulator, and an electric heater. The plate body defines a cavity therewithin. The plate body has on its bottom two openings, which communicate with the cavity and function as a cooling medium inlet and a cooling medium outlet, respectively. The outer periphery of the plate body is covered with the heat insulator. That prevents heat intrusion and/or dissipation from the outer periphery of the plate body in transferring heat between the mounting face and a heat transfer medium within the cavity. That reduces the thermal influence on the mounting face, thereby ensuring more uniform temperature distribution on the mounting face.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to thermostats and testing machines, andmore specifically to a thermostat (so-called “a thermal plate”) for usein testing performance of a semiconductor wafer, on which an electroniccircuit is formed, and to a testing machine provided with thethermostat.

2. Description of the Related Art

Electronic devices as typified by a mobile phone and a personal computerare in widespread use. Recently, these electronic devices are used forvarious purposes or in various environments. That is why environmenttests should be conducted on the electronic devices themselves or theircomponents such as integrated circuits. A thermostat called a “thermalplate” is used as a device for exposing these electronic devices orcomponents to a high-temperature or low-temperature environment.

A common thermal plate has a configuration shown in FIG. 9. A thermalplate 51 shown in FIG. 9 has a plate body 52 and an electric heater 55.The plate body 52 is of a flat columnar shape and has a top facefunctioning as a mounting face 57 on which an article to be tested isplaced or held. Further, the plate body 52 defines therewithin a cavity58 into which a heat transfer medium is introduced. The electric heater55 is provided in thermal contact with the bottom of the plate body 52so as to increase temperature of the mounting face 57. Both controllingof the electric heater 55 and introduction of a heat transfer mediuminto the cavity 58 keep the temperature of the mounting face 57 at adesired temperature. In order to keep the temperature of the mountingface 57 at a lower temperature, for example, a low-temperature fluid isintroduced into the cavity 58. In this way, electronic devices or theircomponents placed or fixed on the mounting face 57 can be exposed to ahigh-temperature or low-temperature environment.

A testing machine provided with a thermal plate or a thermostat having aconfiguration disclosed in the below-listed patent document 1 or 2 isknown. The testing machine disclosed in the patent documents 1 and 2each include a thermal plate (so called a “temperature controlledchuck”) and conduct tests with a semiconductor wafer placed or fixed onthe thermal plate.

Patent Document 1: JP 2005-45039 A

Patent Document 2: JP 10-288646 A

SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

A thermal plate is used for changing temperature of an article such asan integrated circuit placed on a mounting face so as to conductpredetermined tests. Thus, it is preferable to show much lesstemperature variation across the mounting face of the thermal plate.Those skilled in the art are therefore most interested in temperaturevariation across the mounting face. That is why studies or measures tolessen temperature variation across the mounting face are executed. Thethermal plate disclosed in the patent document 1, for example, suppliesa cooling medium to a specific location so as to lessen temperaturevariation. This thermal plate achieves smaller temperature variationthan one previous thereto. However, temperature variation across amounting face is fundamental performance of a thermal plate as describedabove. In the marketplace, such a thermal plate as showing lesstemperature variation has been desired.

The present invention aims to provide a thermal plate or a thermostatshowing less temperature variation across a mounting face on which anarticle is placed.

MEANS TO SOLVE THE PROBLEM

An aspect of the present invention is a thermostat including a platebody having a mounting face on which an article is to be placed or held,further having an outer periphery, and defining a cavity into which aheat transfer medium is to be introduced, and a heat insulator coveringthe outer periphery of the plate body, the thermostat being adapted toadjust temperature of the mounting face at a predetermined temperatureby introduction of a heat transfer medium into the cavity.

Thus, the thermostat of the present aspect prevents heat intrusionand/or dissipation from the outer periphery of the plate body intransferring heat between the mounting face and a heat transfer mediumwithin the cavity. That reduces the thermal influence on the mountingface, thereby ensuring more uniform temperature distribution on themounting face.

Preferably, the plate body is of a flat columnar shape with a top faceand a side face, the top face constituting the mounting face, and theside face constituting the outer periphery.

In the thermostat of this preferred aspect, the plate body is of a flatcolumnar shape, so as to ensure more uniform heat transfer between themounting face and the heat transfer medium. That achieves more uniformtemperature distribution on the mounting face.

Preferably, the thermostat further includes a heater for increasingtemperature of the mounting face.

The thermostat of this preferred aspect adjusts temperature of themounting face more accurately and in broader range.

Preferably, the heater is provided in thermal contact with the bottom ofthe plate body.

Another aspect of the present invention is a testing machine providedwith the thermostat as described above, and having a medium introducingsection for introducing a heat transfer medium, which is at apredetermined temperature, into the cavity.

This aspect relates to a testing machine, which includes the thermostatof the present invention and further includes a medium introducingsection for introducing a heat transfer medium, which is at apredetermined temperature, into the cavity. The testing machine of thepresent aspect achieves more uniform temperature distribution on themounting face of the plate body, thereby conducting environment testsmore accurately on electronic devices or their components.

ADVANTAGEOUS EFFECT OF THE INVENTION

The thermostat of the present invention shows less temperature variationacross the mounting face, thereby providing a testing machine adapted toconduct tests more accurately on electronic devices or their components.

The same can be said to the testing machine of the present invention,which is adapted to conduct tests more accurately on electronic devicesor their components by means of the thermostat showing less temperaturevariation across the mounting face.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a thermal plate (thermostat) of a firstembodiment of the present invention;

FIG. 2 is an exploded perspective view of the thermal plate in FIG. 1;

FIG. 3 is a cross-sectional perspective view of the thermal plate inFIG. 1;

FIG. 4 is a cross section of the thermal plate in FIG. 1 on which asemiconductor wafer is placed;

FIGS. 5A and 5B show a plate body of a thermal plate (thermostat) of asecond embodiment of the present invention, FIG. 5A being a plan viewthereof, and FIG. 5B being a cross section taken along a line A-A inFIG. 5A;

FIG. 6 is a cross-sectional perspective view of the thermal plate of thesecond embodiment of the present invention;

FIG. 7 is a cross section of the thermal plate in FIG. 6 on which asemiconductor wafer is placed;

FIG. 8 is a perspective view of a testing machine of an embodiment ofthe present invention; and

FIG. 9 is an exploded perspective view of a thermal plate in the priorart.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Now, embodiments of the present invention will be described in detailbelow, making reference to the accompanying drawings.

A thermostat (so-called thermal plate) 1 shown in FIGS. 1 to 4 isincorporated in a so-called wafer prober and mainly consists of a platebody 2, a heat insulator 3, and an electric heater 5. The plate body 2is made of metal and of a low and flat columnar shape. The plate body 2has a top face, which functions as a mounting face 7 on which an articlesuch as a semiconductor wafer 15 (FIG. 4) to be tested is placed.

As shown in FIGS. 2 to 4, the plate body 2 defines a cavity 8therewithin. Further, the plate body 2 has a bottom face with twoopenings 11 and 12, which communicate with the cavity 8 so as tointroduce therethrough a cooling medium (heat transfer medium) into thecavity 8. The opening 11 functions as a cooling medium inlet, whereasthe opening 12 functions as a cooling medium outlet. The opening 11 isconnected to a cooling medium introducing section (medium introducingsection for introducing a heat transfer medium) not shown, whereby acooling medium is sent to the opening 11.

Referring to FIGS. 1 to 4, the heat insulator 3 is attached to the platebody 2 so as to cover an outer periphery of the plate body 2. The heatinsulator 3 is of a hollow cylindrical shape and has an inner diameterand height that are substantially identical to an outer diameter andheight, respectively, of the plate body 2. The heat insulator 3 is madeof a material such as a glass wool, a machinable ceramics (for example,well-insulating “Photoveel”: registered trademark of Sumikin Ceramics &Quartz Co., Ltd.). In the thermal plate 1 of the present embodiment, theouter periphery of the plate body 2 is covered with the heat insulator3, which prevents heat intrusion and/or dissipation from the outerperiphery of the plate body 2 in transferring heat between the mountingface 7 and a cooling medium (heat transfer medium) within the cavity 8.That reduces the thermal influence on the mounting face 7, therebyensuring more uniform temperature distribution on the mounting face 7.Herein, in the present embodiment, the heat insulator 3 covers all overthe outer periphery of the plate body 2, but may cover part of theperiphery. The heat insulator 3 may, for example, cover only an upperhalf of the outer periphery of the plate body 2.

As shown in FIG. 2, the electric heater 5 is of a substantially annularshape and has a diameter that is substantially identical to that of thebottom of the plate body 2. The heater 5 is located on a peripheral partof the bottom and in thermal contact with the bottom of the plate body2. In the thermal plate 1, heat generation of the heater 5 and coolingby a cooling medium introduced into the cavity 8 adjust the temperatureof the mounting face 7 that is a surface of the plate body 2.

A semiconductor wafer (article) 15 would be placed on the mounting face7 of the thermal plate 1 of the present embodiment as shown in FIG. 4,for example. Specifically, the semiconductor wafer 15 having a diameterslightly smaller than that of the mounting face 7 is placed onsubstantially the center of the mounting face 7. Actually, the mountingface 7 has a limited area for the semiconductor wafer 15 to be placed.Thus, the semiconductor wafer having a diameter that is identical tothat of the mounting face 7 cannot be placed on the face 7. Herein, themounting face 7 may form a groove or grooves for fixing an article ontothe face, an aperture or apertures for attaching an article undersuction onto the face, or the like.

In the above-mentioned embodiment, the thermal plate 1 includes theheater 5, but the present invention may dispense with the heater 5.

In the above-mentioned embodiment, the plate body 2 has the periphery ofa smoothly curved surface without irregularities, but the presentinvention is not limited thereto and may have a configuration as shownin FIGS. 5A to 7. In FIGS. 5A to 7, the same numerals are assigned tothe same components in FIGS. 1 to 4 for easier comprehension.

In the embodiment shown in FIGS. 5A to 7, a plate body 42 has twodepressed portions 46 a and 46 b all round an outer periphery of theplate body 42. The depressed portions 46 a and 46 b each are an annularU-shaped groove formed by means such as cutting. One depressed portion46 a is formed between the mounting face 7 and the cavity 8 relative toa thickness direction of the plate body 42, whereas the other depressedportion 46 b is formed between the bottom (face opposite to the mountingface 7) and the cavity 8 relative to the thickness direction thereof.Further, the depressed portions 46 a and 46 b both have depths in aradial direction shorter than a distance between the outer periphery ofthe plate body 42 and a side wall of the cavity 8.

In the present embodiment, the heat insulator 3 is formed around theplate body 42, thereby allowing part of the heat insulator 3 to fit intothe depressed portions 46 a and 46 b, as shown in FIGS. 6 and 7. Thatgives an increased sealing performance of the heat insulator 3. In thecase such as deterioration of the heat insulator 3, the heat insulator 3is easily renewed. Further, the present embodiment forms the depressedportions 46 a and 46 b around the outer circumference of the plate body42, so as to reduce the thermal influence (heat intrusion and/ordissipation, for example) from the outer circumference onto the heatconduction between the mounting face 7 and the cavity 8, therebyensuring more uniform temperature distribution on the mounting face 7.

Now, a testing machine will be described below. FIG. 8 is a perspectiveview of a testing machine of an embodiment of the present invention. Asshown in FIG. 8, a testing machine 20 of the present embodiment isroughly divided into two devices, more specifically, into a testingsection 23 incorporating the thermal plate 1 and a gas supplying device(medium introducing section for introducing a heat transfer medium) 25.The testing section 23 and the supplying device 25 are connectedtherebetween by an inlet connecting pipe 27 and an outlet connectingpipe 28. The supplying device 25 incorporates a cooling element so as tocool air. The testing section 23 belongs to a wafer prober.

The thermal plate 1 is housed in a casing 32 that is independent of thesupplying device 25. The casing 32 has therein two pipes, which connectthe inlet connecting pipe 27 to the opening 11 (FIGS. 2 to 4) and theoutlet connecting pipe 28 to the other opening 12 (FIGS. 2 to 4),respectively. Cooled air is introduced into the cavity 8 through theopening 11 from the supplying device 25. Heat generation by the heater 5(FIGS. 1 to 4) and cooling by the cooled air having been introduced intothe cavity 8 adjust temperature of the mounting face 7. Temperature andflow rate of the cooled air to be introduced into the cavity 8 andoutput of the heater 5 are regulated so that temperature of the mountingface 7 is adjustable at least in the range from minus 70 degreesCentigrade to 200 degrees Centigrade.

As described above, since the thermal plate 1 has the heat insulator 3around the plate body 2, the testing machine 20 achieves more uniformtemperature distribution on the mounting face 7. According to thetesting machine 20 of the present embodiment, tests for a component suchas a semiconductor wafer are conducted with a higher degree of accuracy.The thermal plate 1 is placed on an XY table 35 and is movable in X andY directions by a motor not shown.

In the present embodiment, the heat transfer medium to be introducedinto the cavity 8 is a cooled air, but is not particularly limitedthereto only if the medium is a fluid, and may have no preferencebetween a cooling fluid and a heating fluid.

The present embodiment employs the thermal plate 1 shown in FIGS. 1 to4, but may employ a thermal plate 41 shown in FIGS. 5A to 7.

1. A thermostat comprising: a plate body having a mounting face on whichan article is placed or held, further having an outer periphery, anddefining a cavity into which a heat transfer medium is to be introduced;and a heat insulator covering the outer periphery of the plate body, thethermostat being adapted to adjust temperature of the mounting face atpredetermined temperature by introduction of a heat transfer medium intothe cavity.
 2. The thermostat as defined in claim 1, wherein the platebody is of a flat columnar shape with a top face and a side face, thetop face constituting the mounting face, and the side face constitutingthe outer periphery.
 3. The thermostat as defined in claim 1, furthercomprising a heater for increasing temperature of the mounting face. 4.The thermostat as defined in claim 2, further comprising a heater forincreasing temperature of the mounting face.
 5. The thermostat asdefined in claim 4, wherein the heater is provided in thermal contactwith the bottom of the plate body.
 6. A testing machine provided withthe thermostat as defined in claim 1, and having a medium introducingsection for introducing a heat transfer medium, which is at apredetermined temperature, into the cavity.
 7. A testing machineprovided with the thermostat as defined in claim 2, and having a mediumintroducing section for introducing a heat transfer medium, which is ata predetermined temperature, into the cavity.
 8. A testing machineprovided with the thermostat as defined in claim 3, and having a mediumintroducing section for introducing a heat transfer medium, which is ata predetermined temperature, into the cavity.
 9. A testing machineprovided with the thermostat as defined in claim 4, and having a mediumintroducing section for introducing a heat transfer medium, which is ata predetermined temperature, into the cavity.
 10. A testing machineprovided with the thermostat as defined in claim 5, and having a mediumintroducing section for introducing a heat transfer medium, which is ata predetermined temperature, into the cavity.